The increased prevalence of obesity and the lack of treatment success both argue for the design and evaluation of strategies to prevent the development of overweight and obesity. To date, the role of resistance training (RT) in the prevention of overweight and obesity is largely unexplored. RT may have a positive impact on weight management and health as a result of increased fat-free mass (FFM), which may result in increased resting metabolic rate and increased physical activity energy expenditure (i.e., increased total daily energy expenditure). However, the literature relative to the efficacy of RT protocols recommended for healthy adults to alter the aforementioned parameters is inconsistent or inadequately evaluated. We have recently completed a 6 month pilot randomized controlled trial (DK62832) in overweight young adults which evaluated the effect of a supervised minimal RT protocol (3 days/wk, 1 set, 3-6 repetitions maximum, 9 exercises, 11 minutes to complete) on body composition (DEXA), resting and sleeping metabolic rate (whole-room calorimeter). In general, our pilot results suggested a positive impact of RT on body composition and energy expenditure. Based on these results, we propose to conduct a randomized controlled efficacy trial (RT-1 set vs. RT-3 sets vs. non exercise control) to evaluate the potential for a longer intervention (9 months RT with body composition assessments 1 yr post RT completion) with a higher volume of RT (3 sets) to enhance the effects on body composition and energy expenditure observed in the pilot, and to determine the impact of the 2 levels of RT on free-living energy balance (expenditure by doubly labeled water and intake by digital photography and 24-hr recalls). This investigation will be conducted in a sample of healthy, normal and overweight, sedentary, young adult men and women;a group at high risk for development of overweight and obesity. The specific aims of this project are to determine the impact of the volume (1 vs. 3 sets) of a progressive RT protocol for inducing muscular hypertrophy, as recommended by the American College of Sports Medicine, on body weight and body composition (fat mass, FFM, percent body fat) and energy balance. Our results will provide information relative to the minimum volume of RT that may be associated with body weight/fat gain which may inform the development of guidelines for RT to prevent weight gain or to alter body composition. If RT has a favorable impact on energy balance and body composition, it may provide an attractive alternative to aerobic exercise for weight management for busy young adults, as RT requires minimal time, and no need to change clothes or shower (i.e. minimal or no sweating). PUBLIC HEALTH RELEVANCE: The specific aims of this project are to determine the impact of the volume (1 vs. 3 sets) of a progressive resistance training protocol for inducing muscular hypertrophy, as recommended by the American College of Sports Medicine, on body weight and body composition (fat and lean mass), and the balance between energy intake and energy expenditure. Our results will provide information relative to the minimum volume of resistance training that may be associated with body weight/fat gain which may inform the development of guidelines for resistance training to prevent weight gain or to alter body composition. If resistance training has a favorable impact on energy balance and body composition, it may provide an attractive alternative to aerobic exercise for weight management for busy young adults, as resistance training requires minimal time, and no need to change clothes or shower (i.e. minimal or no sweating).